Continued from above post...

I should note that if you were to ever feed your frog a amphibian or reptile that it would have the possibility of carrying diseases. These foods should always be avoided, the only time you would ever have to provoke a feeding response with one of these vertebrates is if you owned let's say like a wc C. Cornuta. Even then you would still be able to force feed before reaching the conclusion of feeding one of these. Or get them to eat a rodent letting them off feeding for a week to get them hungry, they won't avoid food then in the right conditions. Also feeder frogs could secrete poisons into your frog, or as mentioned the diseases those frogs or reptiles adapted to that your frog wasn't ever exposed to.

Feeder fish, should almost always be avoided (Especially goldfish). If you are to buy feeder fish as an occasional variety diet, make sure you buy from a reputable fish store that captive breeds all their fish and confines all of them in clean environments (Flush them of parasites, etc.). Feeder fish that are recommended would be: Guppies, minnows, and shiners contain good nutritional value.

All the above diets (Amphibians, reptiles, feeder fish) have all been known to carry diseases and parasites and that's why they're are almost always avoided.